1. Field of the Invention
My invention relates to simplified sound reproducing apparatus, and more specifically to a phonograph of the type wherein the mechanical vibrations set up in a reproducing stylus by the undulations in a record groove are transmitted, without the process of electrical amplification, to a loudspeaker diaphragm to cause same to produce audible vibrations of the air. Even more specifically, my invention is directed to an improved vibration transmission mechanism in such a phonograph.
2. Description of the Prior Art
According to an example of known phonographs of the above specified type, an intermediate vibrator plate or arm is arranged between a pickup arm and loudspeaker cone or diaphragm, so that the pickup arm travels in sliding contact with the intermediate vibrator during playback for transmission therethrough of stylus vibrations to the diaphragm, as disclosed for example in my U.S. Pat. Nos. 3,589,735 ,3589,735 and 3,773,331. The diaphragm can be either directly mounted on the intermediate vibrator as in the mentioned U.S. patents or, supported as by the phonograph casing, suitably mechanically connected to the intermediate vibrator.
The quality of the sound reproduced by phonographs of such known construction has usually been so poor that they have mostly found use only as playthings for children, either by themselves or by being installed in dolls or the like. The poor sound quality of the phonographs has been more or less taken for granted in such applications. Recently, however, the phonographs have found their way into more sophisticated toys or other devices of educational character. Particularly in this latter application the sound quality of the phonographs stands in need of improvement as far as feasible.
The poor or disagreeable sound quality of the phonographs of the class in question is largely attributable to the fact that the diaphragm in use tends to emphasize high frequency vibrations transmitted thereto, resulting in the production of harshly high-pitched sound. A measure should therefore be taken to limit or reduce the response of the diaphragm to treble frequency vibrations.
I have found that, in the known phonograph construction described previously, the above objective can be accomplished only when the diaphragm is supported by the casing or some other stationary part of the phonograph and connected to the intermediate vibrator via means which limit the transmission of treble frequency vibrations to the diaphragm.
Another problem arises when the diaphragm is supported by such stationary part and mechanically connected to the intermediate vibrator. Since the surface of the record disc or of the turntable used in the phonographs of this class is usually not exactly planar, the reproducing stylus and therefore the intermediate vibrator suffer some slight displacement toward and away from the diaphragm during playback. Further, the diaphragm itself may be displaced toward the intermediate vibrator as a result of some external force applied to the phonograph casing during use. The mechanical connection between the diaphragm and intermediate vibrator must therefore be capable of absorbing such relative displacement thereof toward and away from each other.